Modern Computational Phantoms and Their Applications
Transcript of Modern Computational Phantoms and Their Applications
ModernComputationalPhantomsandTheirApplications
JointICRP-RERF-JHPSWorkshopRecentProgressonRadiationDosimetryforEpidemiologyandRadiologicalProtection
Sunday,December2,2017
WesleyBolch,UniversityofFloridaICRPCommittee2
PresentationObjectives
1. Reviewofdifferentphantomformattypes– stylized,voxel,andhybrid2. CurrentseriesofphantomsusedandadoptedbyICRP– adult,pediatric,andpregnantfemale3. Reviewofdifferentphantommorphometriccategories– phantomlibraries&individual-specific4. Exampleapplicationofphantomlibraries– pediatricCTradiationepidemiology5. FuturephantomsfromtheICRP– polygonmeshformats&toolsforvoxel-to-meshconversion
ComputationalAnatomicPhantomsEssentialtoolfororgandoseassessment
n Definition - Computerizedrepresentationofhumananatomyforuseinradiationtransportsimulationofthemedicalimagingorradiationtherapyprocedure
n Needforphantomsvaryacrossareasofradiologicalprotectionn Establishingdosecoefficientsforinternalradiationexposure
n Specificabsorbedfractionsforbothself-doseandcross-dosetointernalorgansarecomputedusingcomputationalphantoms.TheseSAFvaluesarethenused,alongwithbiokineticmodelsandradionuclidedecayschemes,tocomputedosecoefficients- organequivalentdoseoreffectivedoseperactivityingestedorinhaled
n Establishingdosecoefficientsforexternalradiationexposuren Eitheroccupationalorenvironmentalfieldsofradiationorradionuclideemissions
n Computingorgandosesinradiologicalaccidents– retrospectively/prospectively
ComputationalAnatomicPhantomsEssentialtoolfororgandoseassessment
n Definition - Computerizedrepresentationofhumananatomyforuseinradiationtransportsimulationofthemedicalimagingorradiationtherapyprocedure
n Needforphantomsvarywiththemedicalapplicationn NuclearMedicine
n 3Dpatientimagesgenerallynotavailable,especiallyforchildren
n Diagnosticradiologyandinterventionalfluoroscopyn No3Dimage
n Computedtomographyn 3Dpatientimagesavailable,problem– organsegmentationn Noanatomicinformationatedgesofscancoverage
n Radiotherapyn Neededforcharacterizingout-of-fieldorgandoses
n Examples– IMRTscatter,protontherapyneutrondose
Computational Anatomic PhantomsPhantom Types and Morphometric Categories
n PhantomFormatTypesð Stylized(ormathematical)phantoms
ð Voxel(ortomographic)phantoms
ð Hybrid(orNURBS/PM)phantoms
Stylized(mathematical)phantomsFlexiblebutanatomicallyunrealistic
Voxel(tomographic)phantomsAnatomicallyrealisticbutnotveryflexible
Hybrid(NURBS/PolygonMesh)phantomsBothanatomicallyrealisticandflexible
SegmentationPolygonization
NURBSmodeling Voxelization
SegmentpatientCTimagesusing3D-DOCTORTM
Convertintopolygonmeshusing3D-DOCTORTM
MakeNURBSmodelfrom
polygonmeshusing
RhinocerosTM
ConvertNURBSmodelintovoxelmodelusingMATLABcodeVoxelizer
ExampleoftheprocessusedattheUniversityofFlorida
Voxelizer Algorithm - See Phys Med Biol 52 (12) 3309-3333 (2007)
HybridPhantomConstruction
ComputationalAnatomicPhantomsPhantomTypesandCategories
n PhantomFormatTypesð Stylized(ormathematical)phantoms
ð Voxel(ortomographic)phantoms
ð Hybrid(orNURBS/PM)phantoms
n PhantomMorphometricCategoriesð Reference(50th percentileindividual,patientmatchingbyageonly)
ð Patient-dependent(patientmatchedbynearestheight/weight)
ð Patient-sculpted(patientmatchedtoheight,weight,andbodycontour)
ð Patient-specific(phantomuniquelymatchingpatientmorphometry)
MorphometricCategories– ReferencePhantoms
ReferenceIndividual- AnidealisedmaleorfemalewithcharacteristicsdefinedbytheICRPforthepurposeofradiologicalprotection,andwiththeanatomicalandphysiologicalcharacteristicsdefinedinICRPPublication89(ICRP2002).
Note– Whileorgansize/massarespecified inanICRPreferencephantom,organshape,depth,positionwithinthebodyarenotdefined byreferencevalues
ReferencePhantomsUsedbytheICRPUntilveryrecently,alldosecoefficientspublishedbytheICRPwerebasedoncomputationaldatageneratedusingtheORNLstylizedphantomseries.
ORNLTM-8381Cristy&Eckerman
PublicationsfromICRPusingthePublication110Phantoms• ICRPPublication116– ExternalDoseCoefficients(2010)• ICRUReport84– CosmicRadiationExposuretoAircrew(2010)• ICRPPublication123– AssessmentofRadiationExposureofAstronautsinSpace(2013)
ReferencePhantomsAdoptedbytheICRP
ICRPPublication110– AdultReferenceComputationalPhantoms
PublicationsfromICRPusingthePublication110Phantoms• Publication133- Referencespecificabsorbedfractions(SAF)forinternaldosimetry• Publication130Series- Dosecoefficientsforradionuclideinternaldosimetryfollowinginhalation/ingestion
ReferencePhantomsAdoptedbytheICRPICRPsupcomingreferencephantomsforpediatricindividualsarebasedupontheUF/NCIseriesofhybridphantoms
CurrentPublicationsUnderDevelopmentinICRPCommittee2UsingPediatricPhantoms
TaskGroup90DoseCoefficientsforEnvironmentalExternalExposures
TaskGroup95DoseCoefficientsforEnvironmentalInternalExposures
TaskGroup96SpecificAbsorbedFractionsforInternalExposures
ICRPSeriesofReferenceFetalModels
ICRPSeriesofReferencePregnantFemaleModels
Definition-Expandedlibraryofreferencephantomscoveringarangeofheight/weightpercentiles
NHANES Database7320 individuals
AgeWeightStanding heightSitting heightBMIBiacromial breadthBiiliac breadthArm circumferenceWaist circumferenceButtocks circumferenceThigh circumference
ICRP - based UFHADM
US based phantom library10% 25% 50% 75% 90%
Reference weights @ 1 or more fixed anthropometric parameter(s)NHANES - based
UFHADM
MorphometricCategories– PatientDependentPhantoms
Patient-DependentHybridPhantoms– UFSeries
Geyeretal.– PhysMedBiol(2014)
MorphometricCategories– PatientDependentPhantoms
UF/NCIPhantomLibrary- Children
Phantomforeachheight/weightcombinationfurthermatchingaveragevaluesofbodycircumferencefromCDCsurveydata
85pediatricmales73pediatricfemales
UF/NCIPhantomLibrary- Adults
Phantomforeachheight/weightcombinationfurthermatchingaveragevaluesofbodycircumferencefromCDCsurveydata
100adultmales93adultfemales
ArticlefromBrenneretal.2001whichchangedCTimagingpracticeworldwide
RESULTS.Thelargerdosesandincreasedlifetimeradiationrisksinchildrenproduceasharpincrease,relativetoadults,inestimatedriskfromCT.EstimatedlifetimecancermortalityrisksattributabletotheradiationexposurefromaCTina1-year-oldare0.18%(abdominal)and0.07%(head)—anorderofmagnitudehigherthanforadults—althoughthosefiguresstillrepresentasmallincreaseincancermortalityoverthenaturalbackgroundrate.IntheUnitedStates,ofapproximately600,000abdominalandheadCTexaminationsannuallyperformedinchildrenundertheageof15years,aroughestimateisthat500oftheseindividualsmightultimatelydiefromcancerattributabletotheCTradiation.
Simplisticmethodsoforgandose
ResponsestoBrennerArticle:• Developmentofprofessionalsocietyalliances– ImageGently,StepLightly,GowiththeGuidelines• Developmentofsize-specificandstandardizedimagingprotocols• Developmentofnewtechnologies
• TubecurrentmodulationinCT• Improveddetectortechniques• Improvedimagereconstructionalgorithms
Distinctionbetween…Riskprojection – organdoseestimatescoupledwithexistingcancerriskmodelsRiskassessment– directmeasureofcancerriskthroughepidemiologystudies
UseofCTscansinchildrentodelivercumulativedosesofabout50mGymightalmosttripletheriskofleukaemia anddosesofabout60mGymighttripletheriskofbraincancer.Becausethesecancersarerelativelyrare,thecumulativeabsoluterisksaresmall:inthe10yearsafterthefirstscanforpatientsyoungerthan10years,oneexcesscaseofleukaemia andoneexcesscaseofbraintumour per10000headCTscansisestimatedtooccur.Nevertheless,althoughclinicalbenefi tsshouldoutweighthesmallabsoluterisks,radiationdosesfromCTscansoughttobekeptaslowaspossibleandalternativeprocedures,whichdonotinvolveionising radiation,shouldbeconsideredifappropriate.
TheincreasedincidenceofcancerafterCTscanexposureinthiscohortwasmostlyduetoirradiation.Becausethecancerexcesswasstillcontinuingattheendoffollow-up,theeventuallifetimeriskfromCTscanscannotyetbedetermined.RadiationdosesfromcontemporaryCT scans are likely to be lower than those in 1985-2005, but someincreaseincancerriskisstilllikelyfromcurrentscans.FutureCTscansshouldbelimitedtosituationswherethereisadefiniteclinicalindication,witheveryscanoptimised toprovideadiagnosticCTimageatthelowestpossibleradiationdose.
RiskofPediatricandAdolescentCancerAssociatedwithMedicalImagingR01CA185687
The use of medical imaging that delivers ionizing radiation is high in the United States. The potentialharmful effects of this imaging must be understood so they can be weighed against its diagnosticbenefits, and this is especially critical for our vulnerable populations of children and pregnant women.The proposed study will comprehensively evaluate patterns of medical imaging, cumulative exposureto radiation, and subsequent risk of pediatric cancers in four integrated health care delivery systemscomprising over 7 million enrolled patients enrolled from 1996-2017.
ProjectManagementUniversityofCalifornia,SanFrancisco(UCSF)
BiostatisticsandEpidemiologyUniversityofCalifornia,Davis(UCD)
OrganDoseAssessmentUniversityofFlorida(UF)
PatientEnrollmentSitesKaiserPermanenteNorthernCalifornia(KPNC)KaiserPermanenteNorthWest(KPNW)KaiserPermanenteHawaii(KPHI)KaiserPermanenteWashington(KPWA)MarshfieldClinicResearchInstitute(MCRI)PediatricOncologyGroupofOntario(POGO)GeisingerHealthSystems(GE)HarvardPilgrimHealthPlan(HP)
Aim1:ImagingUtilizationPatternsAim1A– PatternsofimagingutilizationinpregnantwomenAim1B– PatternsofimagingutilizationinchildrenAim1C– Patternsofimagingutilizationinadultsandchildren
Aim2:OrganDoseandAssociationwithCancerOutcomesAim2A– Imaginginpregnantwomen andchildhoodcancerriskAim2B– Imaginginchildren andchildhoodleukemiariskAim2C– Imaginginpregnantwomenandchildren andchildhoodcancerrisk
RiskofPediatricandAdolescentCancerAssociatedwithMedicalImagingR01CA185687
1.OrganDoseReconstructioninComputedTomography
CTProcedureDetailsYearofscanScan#incurrentyearSeries#incurrentscanBodypartimagedMedicalfacilityCTscannermanufacturerCTscannermodel
PatientDataStudyIDAgeGenderHeightWeightEffectivediameteratcenterslice(cm)
PregnantFemalesGestationalage
CTTechniqueFactorsScanlength(cm)Beamcollimation(mm)Beamenergy(kVp)PitchCTDIvol(mGy)DLP(mGy-cm)FixedormodulatedmAExamAveragedmAs
DataCollection– 2006to2017 RadimetricsDataCollection– 1996to2006 DataAbstraction
𝑁𝐹𝐸,𝐶(𝑝ℎ𝑜𝑡𝑜𝑛𝑠𝑚𝐴𝑠 ) =
𝐴𝑖𝑟𝐾𝑒𝑟𝑚𝑎𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 (𝑚𝐺𝑦𝑚𝐴𝑠)
𝐴𝑖𝑟𝐾𝑒𝑟𝑚𝑎𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 (𝑚𝐺𝑦𝑝ℎ𝑜𝑡𝑜𝑛)
1
𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒 +𝑚𝐺𝑦𝑚𝐴𝑠0
= 2 3 𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒𝑖 +𝑚𝐺𝑦𝑝ℎ𝑜𝑡𝑜𝑛0
𝑧𝑒𝑥𝑎𝑚 𝑒𝑛𝑑
𝑖=𝑍𝑒𝑥𝑎𝑚 𝑠𝑡𝑎𝑟𝑡
< × 𝑁𝐹𝐸,𝐶 +𝑝ℎ𝑜𝑡𝑜𝑛𝑠𝑚𝐴𝑠 01
𝑊𝐹(𝑧) = 𝐴𝑉𝑎𝑣𝑒𝑟 𝑎𝑔𝑒 (𝑧)
∑ 𝐴𝑉𝑎𝑣𝑒𝑟𝑎𝑔𝑒 ,𝑖𝑍𝑒𝑥𝑎𝑚 𝑒𝑛𝑑𝑖=𝑍𝑒𝑥𝑎𝑚 𝑠𝑡𝑎𝑟𝑡
1
𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝑚𝐴𝑠 =(𝐸𝑥𝑎𝑚𝐴𝑣𝑒𝑟𝑎𝑔𝑒𝑚𝐴) × 𝑅𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑇𝑖𝑚𝑒(𝑠)
𝐸𝑥𝑎𝑚𝑃𝑖𝑡𝑐ℎ1
𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒(𝑚𝐺𝑦) = 12 𝑂𝑟𝑔𝑎𝑛𝐷𝑜𝑠𝑒𝑖 4𝑚𝐺𝑦𝑚𝐴𝑠
6 ×𝑊𝐹𝑖𝑍𝑒𝑥𝑎𝑚 𝑒𝑛𝑑
𝑖=𝑍𝑒𝑥𝑎𝑚 𝑠𝑡𝑎𝑟𝑡
> × 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝑚𝐴𝑠1
CTcomputationalmethodology– FixedTubeCurrent
CTcomputationalmethodology– ModulatedTubeCurrent
SixMethodsofPatient-to-PhantomMatchingforCTOrganDosimetry
1. PatientAge/GenderOnly UF/NCIReferencePhantom2. HeightandWeight UF/NCILibraryPhantom
3. EffectiveDiameter– ScanAveraged UF/NCILibraryPhantom4. EffectiveDiameter– CenterSlice UF/NCILibraryPhantom
5. WaterEquivalentDiameter– ScanAveraged UF/NCILibraryPhantom6. WaterEquivalentDiameter– CenterSlice UF/NCILibraryPhantom
𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟(𝑐𝑚) =0𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟𝐿𝑎𝑡𝑒𝑟𝑎𝑙 (𝑐𝑚) × 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟𝐴𝑃(𝑐𝑚)1
𝑊𝑎𝑡𝑒𝑟𝐸𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟(𝑐𝑚) = 2561
1000𝐶𝑇(𝑥, 𝑦)𝑅𝑂𝐼AAAAAAAAAAAAAAA + 1C
𝐴𝑅𝑂𝐼(𝑐𝑚2)𝜋
1
𝐶𝑇(𝑥, 𝑦) = *𝜇(𝑥, 𝑦) − 𝜇𝑤𝑎𝑡𝑒𝑟
𝜇𝑤𝑎𝑡 𝑒𝑟2 × 10001 𝜇" = 𝜌 ×'(')𝑤𝑖 ,
𝜇𝜌-𝑖,𝑗𝑝𝑗 1
𝑁𝑒
𝑗
4𝑁𝑐
𝑖
1
AAPMTaskGroup204
AAPMTaskGroup220
BoxplotscomparingorgandosepercentdifferenceforeachofthesixmatchingparametersbasedonCDCBMIclassificationsforpediatricpatients.Theverticallinesextendatmost1.5timestheinterquartilerange.
2.OrganDoseReconstructioninDiagnosticFluoroscopy
FluoroscopyProcedureDetailsProceduretype(1to6)CumulativefluoroscopytimeCumulativereferenceairkermaCumulativekerma-areaproduct
PatientDataStudyIDAgeGenderHeightWeight
ReferenceFluoroscopyExams1.UpperGastrointestinalSeries(UGI)2.UpperGastrointestinalSerieswithFollow-Through(UGI-FT)3.VoidingCystourethrogram(VCUG)4.RehabilitationSwallow(RS)5.LowerGastrointestinalSeries/BariumEnema(LGI)6.GastrostomyTubePlacement(G-Tube)
DataCollection– 2006to2017 RadimetricsDataCollection– 1996to2006 DataAbstraction
Problem – nearlyalldiagnosticfluoroscopysystemscannotgenerateRDSRsSolution – create“reference”diagnosticexamsandscaledosesbyFT,RAK,KAP
DiagnosticFluoroscopyProcedureOutlines- UF
ProcedureDuration:120secondsVCUG
IodineContrast
3.OrganDoseReconstructioninDiagnosticNuclearMedicine
NMProcedureDetailsProceduretype(1to6)AdministeredActivity
PatientDataStudyIDAgeGenderHeightWeight
ReferenceNMProcedures1.Tc-99mDMSA2.Tc-99mMDP3.Tc-99mMAG34.F-18FDG5.Tc-99mSulfurColloid6.I-123MIBG
DataCollection– 2006to2017 RadimetricsDataCollection– 1996to2006 DataAbstraction
Problem – InjectedactivitymightnotbeavailableSolution – Usecurrentguidelinesorperiod-specificweight-baseddosingschemes
Biokinetics – AssumeICRPreferencemodelsRadionuclideSvalues– AssumevaluesfromtheUFreferencephantoms
Committee2TaskGroup103
MRCPs (Mesh-typeReferenceComputationalPhantoms)
VRCPs (Voxel-typeReferenceComputationalPhantoms)
(ICRPPublication110)FigurecourtesyofCHKim– TG103Chair
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FigurecourtesyofCHKim– TG103Chair
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Publication 133 data Mesh phantom-AM (Geant4) Voxel phantom-AM (Geant4)
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ImportantConclusion–
UseofMesh-TypePhantomsDoseNotAlterInAnyMeaningfulWayDoseCoefficientsPreviouslyPublishedbyICRP
n Successfulconversionofvoxelphantomtosurfacemeshedphantomwithuniquevertices
n SurfacemeshreadyforTetgenTM togeneratetetrahedralmesh
n JointcollaborationbetweenUFandJAEA(manuscriptinpreparation)
Recently Developed Voxel to TM Algorithm
Thankyouforyourattention!